diff --git a/embassy-stm32f4-examples/Cargo.toml b/embassy-stm32f4-examples/Cargo.toml
index 6502a77a..72fd6436 100644
--- a/embassy-stm32f4-examples/Cargo.toml
+++ b/embassy-stm32f4-examples/Cargo.toml
@@ -31,9 +31,3 @@ stm32f4xx-hal  = { version = "0.8.3", features = ["rt", "stm32f405"], git = "htt
 futures = { version = "0.3.8", default-features = false, features = ["async-await"] }
 cortex-m-rtic = "0.5"
 rtt-target = { version = "0.3", features = ["cortex-m"] }
-
-
-
-[[bin]]
-name = "serial"
-path = "src/serial.rs"
\ No newline at end of file
diff --git a/embassy-stm32f4-examples/src/serial.rs b/embassy-stm32f4-examples/src/bin/serial.rs
similarity index 90%
rename from embassy-stm32f4-examples/src/serial.rs
rename to embassy-stm32f4-examples/src/bin/serial.rs
index ea049701..f3e0526c 100644
--- a/embassy-stm32f4-examples/src/serial.rs
+++ b/embassy-stm32f4-examples/src/bin/serial.rs
@@ -3,7 +3,9 @@
 #![feature(trait_alias)]
 #![feature(type_alias_impl_trait)]
 
-// extern crate panic_halt;
+#[path = "../example_common.rs"]
+mod example_common;
+use example_common::{panic, *};
 
 use cortex_m::singleton;
 use cortex_m_rt::entry;
@@ -45,7 +47,7 @@ async fn run(dp: stm32::Peripherals, cp: cortex_m::Peripherals) {
     let buf = singleton!(: [u8; 30] = [0; 30]).unwrap();
 
     buf[5] = 0x01;
-    serial.send(buf).await;
+    serial.send(buf).await.unwrap();
 }
 
 static EXECUTOR: Forever<Executor> = Forever::new();
@@ -56,7 +58,7 @@ fn main() -> ! {
     let cp = cortex_m::peripheral::Peripherals::take().unwrap();
 
     let executor = EXECUTOR.put(Executor::new(cortex_m::asm::sev));
-    executor.spawn(run(dp, cp));
+    executor.spawn(run(dp, cp)).unwrap();
 
     loop {
         executor.run();
diff --git a/embassy-stm32f4-examples/src/example_common.rs b/embassy-stm32f4-examples/src/example_common.rs
new file mode 100644
index 00000000..ff4d8575
--- /dev/null
+++ b/embassy-stm32f4-examples/src/example_common.rs
@@ -0,0 +1,17 @@
+#![macro_use]
+
+use defmt_rtt as _; // global logger
+use panic_probe as _;
+
+pub use defmt::*;
+
+use core::sync::atomic::{AtomicUsize, Ordering};
+
+#[defmt::timestamp]
+fn timestamp() -> u64 {
+    static COUNT: AtomicUsize = AtomicUsize::new(0);
+    // NOTE(no-CAS) `timestamps` runs with interrupts disabled
+    let n = COUNT.load(Ordering::Relaxed);
+    COUNT.store(n + 1, Ordering::Relaxed);
+    n as u64
+}
diff --git a/test-build.sh b/test-build.sh
index f67cc5b2..04e1a95e 100755
--- a/test-build.sh
+++ b/test-build.sh
@@ -23,3 +23,8 @@ set -euxo pipefail
 (cd embassy-nrf; cargo build --target thumbv7em-none-eabi --features 52840,log)
 (cd embassy-nrf; cargo build --target thumbv7em-none-eabi --features 52840,defmt)
 
+# embassy-stm32f4
+
+(cd embassy-stm32f4-examples; cargo build --target thumbv7em-none-eabi --bins)
+(cd embassy-stm32f4; cargo build --target thumbv7em-none-eabi --features stm32f405)
+(cd embassy-stm32f4; cargo build --target thumbv7em-none-eabi --features stm32f405,defmt)